Решение:
а) $$sin t = \frac{1}{2}$$ $$t = (-1)^n \frac{\pi}{6} + \pi n, n \in Z$$
б) $$cos t = -\frac{\sqrt{3}}{2}$$ $$t = \pm \frac{5\pi}{6} + 2\pi n, n \in Z$$
Ответ: a) $$t = (-1)^n \frac{\pi}{6} + \pi n, n \in Z$$; б) $$t = \pm \frac{5\pi}{6} + 2\pi n, n \in Z$$